The knowledge of the T.D.C. position in a reciprocating engine is of prime importance in the setting of engine timing conditions. It is generally determined by inserting a linear position gauge in a respective cylinder in a non-firing mode of the engine and slowly rotating the crankshaft until the piston reaches its uppermost limit in the cylinder corresponding to T.D.C. To enable the gauge to be inserted in the cylinder, access has to be provided to the piston crown and this entails removal of cylinder head components. This known procedure is costly and time-consuming.